Until now, wet etching of polycrystalline silicon (polysilicon), both doped and in-situ doped, has been accomplished using chemicals such as choline. Wet etching of silicon nitride has been done using hot phosphoric acid. Both solutions have very fast etch rates for their respective films. Controlled etching of either poly silicon or silicon nitride has been very difficult. Therefore, a need exists for a method of controlled etching of polysilicon and silicon nitride.